Herpes labialis affects approximately one-third of the world population. Lesions associated with the disease are generally recurrent and cause considerable pain and discomfort. Successful treatment of cutaneous herpes infections requires the effective delivery of an active anti-viral agent to the site of viral replication. Treatment failure with an efficacious drug can often be attributed to poor drug release from the delivery vehicle and/or poor skin penetration of the therapeutic agent. This proposal is based on the development of novel drug delivery vehicles for topical treatment of herpes labialis. Specifically, this investigator proposes to formulate and evaluate a series of poloxamer gels as drug delivery vehicles for the treatment of herpes labialis. The availability of poloxamers of varying chain length will allow for the formulation of versatile, cosmetically acceptable drug delivery vehicles possessing varying physico-chemical properties. Acyclovir will be used as a model compound to quantitate the in vitro rate of drug release from various formulations. Formulations exhibiting good release characteristics will be further evaluated in vivo, by determining the rate and extent of percutaneous absorption of acyclovir in rabbits. The study will provide a quantitative basis for the development of an optimal poloxomer gel formulation for acyclovir. Furthermore, the methodology will be established for the evaluation of similar dosage forms for other anti-virals.